The present invention relates to a method of continuously manufacturing thin porous conductive strips by a calendering technique.
It also relates to the product obtained using the method and in particular to the use of the product as an electrode for a fuel cell.
The invention aims to produce continuous porous strips at an industrial rate, which strips may include a plurality of thin layers from about a few microns to a few hundreds of microns thick simply by using a calender and feeding powdered materials into it.
The invention also aims to produce thin homogeneous layers of uniform porosity in which there are no fractures and which are self supporting.
Proposals have already been made to produce strips by calendering powdered material based on carbon powder or on a metal powder with a binder.
However, in most cases, it is necessary to associate a support such as a mesh or a fabric with these materials, the mesh or fabric being embedded after calendering in the layer formed; this causes anisotropy, which may be detrimental to the uses envisaged.
Further, the powdered material is generally conveyed by a conveyor belt which also passes through the calender due to the fact that in general, the layer formed is not self supporting. Such a layer must then undergo heat treatment so as to consolidate it.
In the majority of cases, unless particular precautions are taken requiring the use of complex apparatus for feeding the calender, there occurs a binding phenomenon which results from the mutual adherence of the grains during calendering, which adherence prevents the calender from being fed uniformly and results in lack of homogeneity in the layer produced.
Lastly, this manufacturing method generally entails the use of pore-forming products in the powdered material for obtaining suitable porosity, and the removal of said pore-forming products after calendering may be detrimental to the uses envisaged.
Preferred applications of the present invention make it possible to mitigate the disadvantages described hereinabove.